This invention relates to providing optical scanning and in particular to a method and apparatus which is capable of high resolution line scanning in reading or writing of information.
Optical scanning apparatus are useful for a variety of functions, such as optical printing, document scanning and facsimile reproduction. A continuing need exists in these areas for improvement in resolution. For example, computer printouts are usually provided by impact printers which produce a relatively low resolution. A high quality printout can be produced by photographic techniques, which involve development of a film exposed by CRT projection, but at a fairly high cost.
Laser printers have the potential for providing high resolution at a low cost. Such apparatus utilize a laser beam to scan a rotating drum a line at a time. The drum includes a layer of material on which an electrostatic charge pattern can be formed a line at a time by the scanning action of the laser beam. This charge pattern can then be converted to a visible image on paper or other suitable material. In a typical laser printer, the scanning of the beam is effected by a rotating, multifaceted mirror. (See, e.g., U.S. Pat. No. 3,835,249 issued to Dattilo et al.) While adequate, the resolution of such systems is limited by vibrations and other effects from the motor controlling the rotating mirror. These effects are heightened by the fact that a multifaceted mirror has a limited useful angle of rotation for each line scanned. If the resolution of laser printers could be increased, they could provide a printout with the quality of photographic techniques at a fraction of the cost.
It is therefore a primary object of the invention to provide an optical scanning method and apparatus with increased resolution capabilities.